Method and apparatus for radiative heat transfer augmentation for aviation electronic equipments cooled by convection

ABSTRACT

A method and apparatus for radiative heat transfer augmentation for aviation electronic equipments cooled by forced and/or natural convection are disclosed. In one embodiment, the apparatus includes a first heat dissipation device to dissipate heat from the aviation electronic equipments housed in an aviation electronic equipment rack using forced convection. Further, the apparatus includes a second heat dissipation device to enhance heat dissipation from the aviation electronic equipments by radiation and natural convection. Furthermore, the second heat dissipation device is strategically disposed with respect to aircraft skin and configured to maximize radiative view factor.

RELATED APPLICATIONS

Benefit is claimed under 35 U.S.C. 119(a)-(d) to Indian ProvisionalApplication Serial No. 1757/CHE/2011 entitled “METHOD AND APPARATUS FORRADIATIVE HEAT TRANSFER AUGMENTATION FOR AVIATION ELECTRONIC EQUIPMENTSCOOLED BY CONVECTION” filed on May 24, 2011 by Airbus Engineering CentreIndia.

FIELD OF TECHNOLOGY

Embodiments of the present subject matter relate to dissipating heatfrom electronic equipments. More particularly, embodiments of thepresent subject matter relate to dissipating heat by radiationaugmentation for electronic equipments on board aircraft cooled byforced and/or natural convection.

BACKGROUND

Electronic equipments installed inside aircraft, often contain many heatgenerating components that are housed in racks. Existing techniques forcooling such electronic equipments primarily depend on ventilationsystems based on forced and/or natural convection. Typically,ventilation of such electronic equipments is based on forced airflowfrom the bottom of the racks, which then passes through the electronicequipments. The heated air coming from the electronic equipments is thencollected and exhausted from the aircraft. Such method of heatextraction is generally referred to as “forced ventilation”. Further,the ventilation of such electronic equipments is also based on naturalconvection. Generally, natural convection does not occur due to fluidmotion generated by an external source (e.g., a pump, a fan, a suctiondevice and the like), but occurs due to density difference in the fluidoccurring as a result of temperature gradients.

However, a failure in the forced ventilation system can lead to completedependence of cooling of the electronic equipments by natural convectionand this may not be sufficient and can lead to failure of the electronicequipments.

SUMMARY

A method and apparatus for radiative heat transfer augmentation foraviation electronic equipments cooled by convection are disclosed.According to one aspect of the present subject matter, heat from theaviation electronic equipments housed in an aviation electronicequipment rack is dissipated by forced convection using a first heatdissipation device. Further, heat dissipation from the aviationelectronic equipments by radiation and natural convection is enhancedusing a second heat dissipation device. In one embodiment, the secondheat dissipation device is strategically disposed with respect toaircraft skin and configured to maximize radiative view factor.

According to another aspect of the present subject matter, the apparatusfor radiative heat transfer augmentation for the aviation electronicequipments cooled by forced and/or natural convection includes the firstheat dissipation device to dissipate heat from the aviation electronicequipments housed in the aviation electronic equipment rack using forcedconvection. Further, the apparatus includes the second heat dissipationdevice to enhance heat dissipation from the aviation electronicequipments by natural convection. Furthermore, the second heatdissipation device is strategically disposed with respect to theaircraft skin and configured to maximize radiative view factor.

The methods and apparatuses disclosed herein may be implemented in anymeans for achieving various aspects. Other features will be apparentfrom the accompanying drawings and from the detailed description thatfollow.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are described herein with reference to the drawings,wherein:

FIG. 1 is a side elevation view of an aircraft showing location ofavionics bay, in the context of the invention;

FIG. 2 is an isometric view of the avionics bay in the aircraft, such asthose shown in FIG. 1, in the context of the invention;

FIG. 3 is a schematic showing a radiative heat transfer augmentationtechnique deployed in the aircraft for aviation electronic equipmentscooled by forced and/or natural convection, according to one embodiment;and

FIG. 4 illustrates a flow diagram of an exemplary method for radiativeheat transfer augmentation for the aviation electronic equipments cooledby forced and/or natural convection, such as those shown in FIG. 3,according to one embodiment.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

A method and apparatus for radiative heat transfer augmentation foraviation electronic equipments cooled by convection are disclosed. Inthe following detailed description of the embodiments of the presentsubject matter, reference is made to the accompanying drawings that forma part hereof, and in which are shown by way of illustration specificembodiments in which the present subject matter may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the present subject matter, and it is to beunderstood that other embodiments may be utilized and that changes maybe made without departing from the scope of the present subject matter.The following detailed description is, therefore, not to be taken in alimiting sense, and the scope of the present subject matter is definedby the appended claims.

FIG. 1 is a side elevation view of an aircraft 100 showing location ofavionics bay 102, in the context of the invention. Particularly, FIG. 1illustrates a portion of the aircraft 100 including the avionics bay102, a cockpit 104, a cabin 106 and a cargo bay 108. As shown in FIG. 1,the avionics bay 102 is, typically, located below the cockpit 104.However, one can envision, the avionics bay 102 being located anywhereelse in the aircraft based on the design and configuration of anaircraft. Further as shown in FIG. 1, the avionics bay 102 includesaviation electronic equipments housed in racks 110. For example, theaviation electronic equipments housed in racks 110 can include one ormore aviation electronic equipment racks 110A-N.

Referring now to FIG. 2, an isometric view of the avionics bay 102 inthe aircraft 100, such as those shown in FIG. 1, is illustrated, in thecontext of the invention. Particularly, FIG. 2 illustrates the aviationelectronic equipments housed in racks 110, in the avionics bay 102,including one or more aviation electronic equipment racks 110A-N. Asshown in FIG. 2, each of the aviation electronic equipment racks 110A-Nincludes one or more heat generating aviation electronic equipments.Exemplary aviation electronic equipments include equipments used fornavigation of the aircraft 100, control of other equipments in theaircraft 100 and the like. For example, the aviation electronicequipments can also be arranged in the form of stacks or the aviationelectronic equipments can be placed independently. Further, the aviationelectronic equipments in the aviation electronic equipment racks 110A-Nare cooled by forced and/or natural convection.

In operation, the aviation electronic equipment racks 110A-N are cooledusing sources of cold air 202A-N in each of the aviation electronicequipment racks 110A-N, respectively, as shown in FIG. 2. Further, thecold air is passed through the aviation electronic equipments in theaviation electronic equipment racks 110A-N to extract the heat from theaviation electronic equipments and is output as hot air. Furthermore asshown in FIG. 2, the hot air is collected, from the aviation electronicequipment racks 110A-N, in collectors for disposing hot air 204A-N ineach of the aviation electronic equipment racks 110A-N, respectively.This is explained in more detail with reference to FIG. 3.

Referring now to FIG. 3, a schematic 300 shows a radiative heat transferaugmentation technique deployed in the aircraft 100 for an aviationelectronic equipment rack 322 cooled by forced and/or naturalconvection, according to one embodiment. Particularly, FIG. 3illustrates a first heat dissipation device 320 and a second heatdissipation device for cooling the aviation electronic equipment rack322. In one embodiment, the second heat dissipation device includes anexternal thermal radiator 308 and one or more heat pipes 310A-C.

As shown in FIG. 3, the first heat dissipation device 320 includes theaviation electronic equipment rack 322, a collector for disposing hotair 304 and a source of cold air 306. For example, the aviationelectronic equipment rack 322 can include any one of the aviationelectronic equipment racks 110A-N, shown in FIG. 2. Further, thecollector for disposing hot air 304 and the source of cold air 306 caninclude any of the corresponding sources of cold air 202A-N and thecollectors for disposing hot air 204A-N associated with the aviationelectronic equipment racks 110A-N, as shown in FIG. 2.

Further as shown in FIG. 3, the aviation electronic equipment rack 322includes a plurality of hot units 312A-F. Exemplary hot units 312A-Finclude the heat generating aviation electronic equipments, as shown inthe aviation electronic equipment racks 110A-N in FIG. 2. However, onecan envision a hot unit in aviation electronic equipments arranged inthe form of stacks or an aviation electronic equipment placedindependently. Furthermore as shown in FIG. 3, each of the hot units312A-F include one or more hot spots H314A1-AN, H314B1-BN, H314C1-CN,H314D1-DN, H314E1-EN and H314F1-FN, respectively. The hot spots in thehot units 312A-F are heat generating areas in the hot units 312A-F.

In operation, the first heat dissipation device 320 dissipates heat fromthe hot units 312A-F housed in the aviation electronic equipment rack322 using forced convection. In dissipating heat from the hot units312A-F, the first heat dissipation device 320 uses cold air streams 316capable of causing forced ventilation. As shown in FIG. 3, the source ofcold air 306 injects cold air streams 316 into the hot units 312A-F.Further as shown in FIG. 3, the arrows coming from the source of coldair 306 and into the hot units 312A-F indicate the direction of the coldair streams 316.

Further in operation, the cold air streams 316 pass through the hotspots in the hot units 312A-F and is output as hot air streams 318. Asshown in FIG. 3, the dotted line arrows coming from the hot units 312A-Findicate the direction of the hot air streams 318. Furthermore inoperation, the hot air streams 318 are collected by the collector fordisposing hot air 304. Moreover, the collector for disposing hot air 304is connected to ventilation ducts for extracting the hot air streams 318from the avionics bay 102, shown in FIG. 2, and disposing the hot airstreams 318 outside the aircraft 100. In addition to heat dissipation byforced convection, the first heat dissipation device 320 also dissipatesheat from the aviation electronic equipment rack 322 by naturalconvection, in thermal contact with the hot spots in the hot units312A-F, shown in FIG. 3.

In one embodiment, the second heat dissipation device, which includesthe external thermal radiator 308 and the heat pipes 310A-C, enhancesheat dissipation from the hot units 312A-F by natural convection andradiation. In this embodiment, the external thermal radiator 308 isstrategically disposed with respect to aircraft skin 302 to maximizeradiative heat dissipation from the hot units 312A-F. As shown in FIG.3, the external thermal radiator 308 includes heat collectors that arecoupled to the hot spots in the hot units 312A-F using thermalconductors. In this embodiment, the thermal conductors are the heatpipes 310A-C, shown in FIG. 3. The heat pipes 310A-C have high thermalconductivity in the longitudinal direction. Further in this embodiment,the heat pipes 310A-C are connected to the hot spots of the hot units312A-F to facilitate the heat transfer from the hot units 312A-F to theexternal thermal radiator 308.

Furthermore in this embodiment, the external thermal radiator 308 issized to complement the cooling provided by the first heat dissipationdevice 320 when the ventilation provided by the forced convection islost. Also, the external thermal radiator 308 is configured to maximizeheat dissipation by radiation and to obtain high radiative view factor.The radiative view factor is the fraction of radiation heat leaving theexternal thermal radiator 308 which is incident on the aircraft skin302. In this embodiment, the external thermal radiator 308 is locatedand oriented in such a way that the radiative view factor is maximized.Also in this embodiment, the hot units 312A-F are strategically disposedin the avionics bay 102 to maximize the radiative view factor with theaircraft skin 302.

Generally, when the aircraft 100 is cruising, the aircraft skin 302 isat a very low temperature. Therefore, the temperature difference betweenthe aircraft skin 302 and the surface of the external thermal radiator308 is very high. As a result, the heat dissipated by radiation from theexternal thermal radiator 308 to the aircraft skin 302 is maximized.Further, the heat is transferred from the external thermal radiator 308in two modes, which include radiation and convection. The heattransferred from the external thermal radiator 308 by radiation istransferred to the aircraft skin 302 and the heat transferred from theexternal thermal radiator 308 by convection is transferred to thesurrounding air. Further, the heat transferred from the external thermalradiator 308 by radiation can be computed using equation:

q _(radiation) =εAσF(T ⁴ _(surface) −T ⁴ _(skin))  (1)

wherein,

q_(radiation) is radiative heat transfer rate;

ε is an emissivity of the surface;

A is area of emitting surface;

σ is the Stefan-Boltzmann Constant;

T_(surface) is an absolute temperature of emitting surface of theexternal thermal radiator 308 (K);

T_(skin) is an absolute temperature of the aircraft skin 302 (K); and

F is a radiative view factor from the surface of the external thermalradiator 308 to the aircraft skin 302.

Furthermore, the heat transferred from the external thermal radiator 308by convection can be computed using equation:

q _(convection) =hA(T _(surface) −T _(reference))  (2)

wherein,

q_(convection) is convective heat transfer rate;

h is the heat transfer coefficient; and

T_(reference) is an absolute temperature of surrounding air (K).

It can be seen from the equation (2) that convective heat transfer isproportional to the difference between the temperature of the emittingsurface of the external thermal radiator 308 and the surrounding air.Further, it can be seen from the equation (1) that radiative heattransfer is proportional to difference in fourth power of temperaturevalues of the aircraft skin 302 and the external thermal radiator 308.Therefore, it can be seen that, higher the difference in temperaturebetween the aircraft skin 302 and the external thermal radiator 308, thehigher is the radiative heat flux. The large temperature differencebetween the aircraft skin 302 and the external thermal radiator 308while the aircraft 100 is cruising results in the radiative heattransfer dominating the convective heat transfer. Since the heattransferred from the external thermal radiator 308 by radiation istransferred to the aircraft skin 302, the temperature of the surroundingair is not increased. This effectively increases the temperaturedifference between the emitting surface of the external thermal radiator308 and the surrounding air resulting in higher convective heat transferrates.

Typically, radiative heat transfer increases the temperature of thesurrounding air when the surrounding air has high humidity content.However, in this embodiment, the participation of humidity in theradiative heat transfer is negligible as humidity level in the avionicsbay 102, shown in FIG. 2, while the aircraft is cruising, is typicallyvery low. Hence, the heat transfer between the external thermal radiator308 and the aircraft skin 302 does not result in an increase in thesurrounding air temperature in the avionics bay 102, shown in FIG. 1.

Referring now to FIG. 4, which illustrates a flow diagram 400 of anexemplary method for radiative heat transfer augmentation for theaviation electronic equipment rack 322 cooled by forced and/or naturalconvection, such as those shown in FIG. 3, according to an embodiment.At block 402, heat is dissipated from the aviation electronic equipmentshoused in the aviation electronic equipment rack by forced convectionusing a first heat dissipation device. In dissipating heat from theaviation electronic equipments, the first heat dissipation device usesair stream capable of causing forced ventilation. Further in dissipatingheat from the aviation electronic equipments, the first heat dissipationdevice cools the aviation electronic equipments by natural and forcedconvection in thermal contact with one or more hot spots of the aviationelectronic equipments. This is explained in more detail with referenceto FIG. 3.

At block 404, heat dissipation from the aviation electronic equipmentsby radiation and natural convection is enhanced using a second heatdissipation device. In this embodiment, the second heat dissipationdevice is strategically disposed with respect to the aircraft skin andconfigured to maximize radiative view factor. Further in thisembodiment, the second heat dissipation device is an external thermalradiator. Furthermore, the external thermal radiator includes a heatcollector that is coupled to the one or more heat spots of the aviationelectronic equipments using thermal conductors. The thermal conductorsare heat pipes having high thermal conductivity in the longitudinaldirection. This is explained in more detail with reference to FIG. 3.

In addition in this embodiment, the second heat dissipation device issized to complement the cooling provided by the first heat dissipationdevice should the forced convection be lost. Also in this embodiment,the second heat dissipation device is disposed with respect to theaircraft skin to maximize heat dissipation by radiation.

In various embodiments, the methods and systems described in FIGS. 1through 4 enable extracting heat from the aviation electronic equipmentracks in the avionics bay using the external thermal radiator whichincreases the radiation heat transfer to the aircraft skin. Further, themethod described in FIGS. 1 through 4 enable substantially eliminatingheat transferred to the surrounding air in the avionics bay.

Although the present embodiments have been described with reference tospecific example embodiments, it will be evident that variousmodifications and changes may be made to these embodiments withoutdeparting from the broader spirit and scope of the various embodiments.Furthermore, the various devices, modules, analyzers, generators, andthe like described herein may be enabled and operated using hardwarecircuitry, for example, complementary metal oxide semiconductor basedlogic circuitry, firmware, software and/or any combination of hardware,firmware, and/or software embodied in a machine readable medium. Forexample, the various electrical structure and methods may be embodiedusing transistors, logic gates, and electrical circuits, such asapplication specific integrated circuit.

1. An apparatus for radiative heat transfer augmentation for aviationelectronic equipments cooled by convection, comprising: a first heatdissipation device to dissipate heat from the aviation electronicequipments housed in an aviation electronic equipment rack using forcedconvection; and a second heat dissipation device strategically disposedwith respect to aircraft skin and configured to maximize radiative viewfactor to enhance heat dissipation from the aviation electronicequipments by radiation and natural convection.
 2. The apparatus ofclaim 1, wherein the first heat dissipation device dissipates heat fromthe aviation electronic equipments using air stream capable of causingforced ventilation.
 3. The apparatus of claim 1, wherein the first heatdissipation device cools the aviation electronic equipments by naturaland forced convection in thermal contact with one or more hot spots ofthe aviation electronic equipments.
 4. The apparatus of claim 1, whereinthe second heat dissipation device is an external thermal radiator. 5.The apparatus of claim 4, wherein the external thermal radiatorcomprises a heat collector that is coupled to the one or more heat spotsof the aviation electronic equipments using thermal conductors.
 6. Theapparatus of claim 5, wherein the thermal conductors are heat pipes. 7.The apparatus of claim 5, wherein the heat pipes have high thermalconductivity in the longitudinal direction.
 8. The apparatus of claim 1,wherein the second heat dissipation device is sized to complement thecooling provided by the first heat dissipation device should the forcedconvection be lost and wherein the second heat dissipation device isdisposed with respect to the aircraft skin to maximize heat dissipationby radiation.
 9. A method of radiative heat transfer augmentation foraviation electronic equipments cooled by forced and/or naturalconvection, comprising: dissipating heat from the aviation electronicequipments housed in an aviation electronic equipment rack by forcedconvection using a first heat dissipation device; and enhancing heatdissipation from the aviation electronic equipments by radiation andnatural convection using a second heat dissipation device, wherein thesecond heat dissipation device is strategically disposed with respect toaircraft skin and configured to maximize radiative view factor.
 10. Themethod of claim 9, wherein, in dissipating heat from the aviationelectronic equipments, the first heat dissipation device dissipates heatfrom the aviation electronic equipments using air stream capable ofcausing forced ventilation.
 11. The method of claim 9, wherein, indissipating heat from the aviation electronic equipments, the first heatdissipation device cools the aviation electronic equipments by naturaland forced convection in thermal contact with one or more hot spots ofthe aviation electronic equipments.
 12. The method of claim 9, whereinthe second heat dissipation device is an external thermal radiator. 13.The method of claim 12, wherein the external thermal radiator comprisesa heat collector that is coupled to the one or more hot spots of theaviation electronic equipments using thermal conductors.
 14. The methodof claim 13, wherein the thermal conductors are heat pipes.
 15. Themethod of claim 13, wherein the heat pipes have high thermalconductivity in the longitudinal direction.
 16. The method of claim 9,wherein the second heat dissipation device is sized to complement thecooling provided by the first heat dissipation device should the forcedconvection be lost and wherein the second heat dissipation device isdisposed with respect to the aircraft skin to maximize heat dissipationby radiation.